For the past two years, Sony Mobile could be counted on to introduce new Xperia smartphone lines at CES -- the S and Z, specifically. Not so this year, as the company's instead offering twists on previously announced hardware, which, for the US market, results in the Xperia Z1S for T-Mobile. If you followed our IFA coverage from last summer, you'll be familiar with what Sony and exclusive US partner T-Mobile have to offer. The Xperia Z1S, set for release January 22nd at $528 outright or $22/mo, retains much of its Z1 counterpart's spec load -- 5-inch, 1080p Triluminos display, Snapdragon 800, 3,000mAh battery and 20.7-megapixel camera -- albeit with some notable upgrades.

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Sony Xperia Z1S

Despite maintaining the same 5-inch screen size as its Z brethren, the Z1S is significantly taller, owing to the larger 3,000mAh battery inside and packs 32GB of storage. Though its lack of an IPS display means viewing angles won't be as generous, the Z1S does feature X-Reality Engine (disabled by default) for improved contrast in stills and video.

The device's now also rated for IP58 certification, making it waterproof, not just splash-resistant, at a depth of up to four and a half feet for about 30 minutes. As for its build, the Z1S still features the "omnibalance" design (that all-around flat-sided look) Sony ushered in with the Z, but here the edges have been gently rounded with a plastic trim, making for a much more comfortable in-hand feel. It's a change we wish had been present from the very start of this Xperia Z line.

Much like its predecessors, the Xperia Z1S' ports are all tucked away behind flaps, with one exception: the headphone jack. At the behest of T-Mobile, that jack, newly centered on the top of the device, has now been made fully accessible when submerged, so users can laze about the pool and not worry about water damage. That's not the only functional change Sony's made to the cosmetics; it's also added in a dual-detent camera key that should make taking shots when submerged in water far easier to do.

With a 20.7-megapixel, f/2.0 camera module on deck and associated software suite, it's clear Sony's placing heavy emphasis on the Xperia Z1S' imaging capabilities. Like its Z1 mate, this US iteration will ship with a specially designed, larger Exmor RS sensor that Sony claims is on par with that of its compact camera line. That's in addition to the G Lens (Sony's in-house solution) and BIONZ for mobile image processing which, together, should translate into faster autofocus, better white balance and images with less blur and discernible noise.

Sony's loading up the Xperia Z1S with the PlayStation App (a first for the Xperia line) and a suite of camera apps to complement that imaging prowess; the same camera apps we saw on the Z1. Of the bunch (i.e., InfoEye, AR Effects, Social Live and TimeShift Burst), only Background Defocus, an app that creates artificial bokeh or background blur, is new and exclusive to the Z1S. Users can also augment this app suite with a selection of third-party add-ons, searchable from within the camera app.

The Xperia Z1S is set for an official nationwide launch on January 22nd, but die-hard Sony fans will have a chance to snag it even sooner than that. An online pre-sale will go live on January 13th, although sadly there is no special purple version on offer. The Z1S comes in black and only black -- for now, anyway.